US11239900B2 - Interference canceller and method for cancelling interference - Google Patents
Interference canceller and method for cancelling interference Download PDFInfo
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- US11239900B2 US11239900B2 US17/120,401 US202017120401A US11239900B2 US 11239900 B2 US11239900 B2 US 11239900B2 US 202017120401 A US202017120401 A US 202017120401A US 11239900 B2 US11239900 B2 US 11239900B2
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/04—Control of transmission; Equalising
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/155—Ground-based stations
- H04B7/15564—Relay station antennae loop interference reduction
- H04B7/15585—Relay station antennae loop interference reduction by interference cancellation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
- H04B1/7103—Interference-related aspects the interference being multiple access interference
- H04B1/7105—Joint detection techniques, e.g. linear detectors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/32—Reducing cross-talk, e.g. by compensating
Definitions
- the present disclosure relates to an interference canceller and interference cancelling method, especially to an interference canceller and interference cancelling method for a network device.
- the transmission signal from a transmitter of a network device can interfere with the reception signal of a receiver of the same network device.
- conventional methods rely on a cancellation signal generation circuit (e.g., a circuit using a least mean square (LMS) technique) of a network device to track and compensate aliasing of an interference signal and a phase shift between a cancellation signal and the interference signal within a certain period of time, and thus the cancellation signal generation circuit may have worse performance due to a timing difference between a transmitter and a receiver of the network device reaching a certain level.
- LMS least mean square
- the cancellation signal generation circuit may be incapable of tracking variations in the phase shift, and this leads to the cancellation signal generation circuit being incapable of generating a suitable cancellation signal at the moment that the network device is leaving the quiet state and thus causing a signal-to-noise ratio of the receiver to deteriorate.
- EEE Energy-Efficient Ethernet
- An object of the present disclosure is to provide an interference canceller and a method for cancelling interference that can tackling an interference problem caused by a transmission signal.
- An embodiment of the interference canceller is operable to generate a cancellation signal for reducing cross port alien near-end (XPAN) crosstalk of a reception signal received by a receiver of a network device.
- This embodiment includes an oversampling circuit, a clock difference calculating circuit, a sample rate converter, and a cancelling circuit.
- the oversampling circuit is configured to oversample an XPAN transmission signal originated from a transmitter of the network device and thereby generate an oversampled signal having a frequency higher than a frequency of a reception clock of the receiver.
- the clock difference calculating circuit is configured to calculate a clock difference between a transmission clock of the transmitter and the reception clock of the receiver.
- the sample rate converter is configured to process the oversampled signal according to the clock difference and thereby generate a conversion signal having a frequency lower than the frequency of the oversampled signal and equal to the frequency of the reception clock of the receiver.
- the cancelling circuit is configured to generate the cancellation signal according to the conversion signal and to determine at least one coefficient of the cancelling circuit according to an error signal dependent on a difference between the XPAN crosstalk of the reception signal and the cancellation signal.
- An embodiment of the method for cancelling interference is performed by a network device.
- This embodiment can generate a cancellation signal for reducing cross port alien near-end (XPAN) crosstalk of a reception signal received by a receiver of the network device, and includes the following steps: oversampling an XPAN transmission signal originated from a transmitter of the network device and thereby generating an oversampled signal having a frequency higher than a frequency of a reception clock of the receiver; calculating a clock difference between a transmission clock of the transmitter and the reception clock of the receiver; processing the oversampled signal according to the clock difference and thereby generating a conversion signal having a frequency lower than the frequency of the oversampled signal and equal to the frequency of the reception clock; and using a filter to generate the cancellation signal according to the conversion signal and to determine at least one coefficient of the filter according to an error signal dependent on a difference between the XPAN crosstalk of the reception signal and the cancellation signal.
- XPAN cross port alien near-end
- FIG. 1 shows a network device including an interference canceller according to an embodiment of the present disclosure.
- FIG. 2 shows an embodiment of the interference canceller of the present disclosure.
- FIG. 3 shows an embodiment of the sample rate converter of FIG. 2 .
- FIG. 4 shows an example of the signal correspondence relation between the oversampled signal and the conversion signal of FIG. 3 .
- FIG. 5 shows another example of the signal correspondence relation between the oversampled signal and the conversion signal of FIG. 3 .
- FIG. 6 shows an embodiment of the receiver mentioned in FIG. 2 .
- FIG. 7 shows another embodiment of the interference canceller of the present disclosure.
- FIG. 8 a shows an example of the energy variation trends of the conversion signal and the XPAN transmission signal of FIG. 7 .
- FIG. 8 b shows another example of the energy variation trends of the conversion signal and the XPAN transmission signal of FIG. 7 .
- FIG. 9 shows an exemplary implementation of the steps performed by the calculation and statistics circuit of FIG. 7 .
- FIG. 10 shows another exemplary implementation of the steps performed by the calculation and statistics circuit of FIG. 7 .
- FIG. 11 shows a method for cancelling interference according to an embodiment of the present disclosure.
- the present disclosure includes an interference canceller and a method for cancelling interference.
- the interference canceller and the method can be applied to a network device including a transmitter and a receiver, and can achieve good performance of interference cancellation when a timing difference between the transmitter and the receiver is serious.
- the interference canceller and the method can track the variation in a relation between an interference signal and a cancellation signal during the quiet state of the low power idle mode of Energy-Efficient Ethernet (EEE) to ensure that the performance of interference cancellation remains good at the moment the network device leaving the quiet state of the low power idle mode.
- EEE Energy-Efficient Ethernet
- FIG. 1 shows a network device including the interference canceller of the present disclosure.
- the network device 100 is an example for understanding, and includes a digital transmission circuit 110 , an analog transmission circuit 120 including a digital-to-analog converter (not shown), a hybrid circuit 130 , an analog reception circuit 140 including an analog-to-digital converter (not shown), a digital reception circuit 150 , and an interference canceller 160 .
- Both the digital transmission circuit 110 and the analog transmission circuit 120 are included in a transmitter, which operates in a first clock domain, of a first transceiver; both the analog reception circuit 140 and the digital reception circuit 150 are included in a receiver, which operates in a second clock domain, of a second receiver; and the first transceiver and the second transceiver are different transceivers, and the first clock domain is different from the second clock domain.
- the interference canceller 160 outputs a cancellation signal to the digital reception circuit 150 according to an output signal of the digital transmission circuit 110 and a feedback signal of the digital reception circuit 150 so that the digital reception circuit 150 can eliminate an interference component of a reception signal from the analog reception circuit 140 according to the cancellation signal.
- FIG. 2 shows an embodiment of the interference canceller of the present disclosure.
- the interference canceller 200 of FIG. 2 is operable to generate a cancellation signal for reducing cross port alien near-end (XPAN) crosstalk of a reception signal (e.g., the output from the analog reception circuit 140 of FIG. 1 ) received by a receiver of a network device.
- the interference canceller 200 includes an oversampling circuit 210 , a clock difference calculating circuit 220 , a sample rate converter 230 , and a cancelling circuit 240 , wherein the oversampling circuit 210 , the clock difference calculating circuit 220 , and the sample rate converter 230 as a whole can be deemed a symbol rate converter.
- the oversampling circuit 210 is configured to oversample an XPAN transmission signal (TX XPAN ) (e.g., the output from the digital transmission circuit 110 of FIG. 1 ) originated from a transmitter of the network device and thereby generate an oversampled signal (TX XPAN_UP ).
- the oversampled signal has a frequency higher than a frequency of a reception clock (RX CLK ) of the receiver; and this feature makes the output (SRC OUT ) of the sample rate converter 230 include aliasing so that the cancelling circuit 240 can generate aliasing similar to the aliasing of the reception signal for interference cancellation.
- the clock difference calculating circuit 220 is configured to calculate a clock difference (CLK DIFF ) between a transmission clock (TX CLK ) of the transmitter and the reception clock of the receiver.
- the sample rate converter 230 is configured to process the oversampled signal according to the clock difference and thereby generate a conversion signal (SRC OUT ).
- the conversion signal has a frequency lower than the frequency of the oversampled signal and equal to the frequency of the reception clock of the receiver in order to eliminate/reduce the phase shift between the XPAN transmission signal and the reception signal.
- the cancelling circuit 240 is configured to generate the cancellation signal (XPAN CANCEL ) according to the conversion signal, and to determine at least one coefficient of the cancelling circuit 240 according to an error signal (S ERROR ) and thereby try to reduce the error which the next error signal will indicate, wherein the error signal is dependent upon the difference between the XPAN crosstalk of the reception signal and the cancellation signal as shown in FIG. 6 .
- the oversampling circuit 210 of FIG. 2 can use a known technique (e.g., a zero-order hold technique or a raised cosine technique) or a self-developed technique to oversample the XPAN transmission signal; for example, a zero-order hold technique can duplicate an input signal (e.g., a signal having input values “AB”) and generate an output signal (e.g., a signal having output values “AABB”) to realize an oversampling operation.
- a zero-order hold technique can duplicate an input signal (e.g., a signal having input values “AB”) and generate an output signal (e.g., a signal having output values “AABB”) to realize an oversampling operation.
- the network device e.g., the network device 100 of FIG.
- the interference canceller of the present disclosure is an Ethernet network device conforming to the 2.5G BASE-T standard; a receiver of the network device receives reception signals via a connection terminal (e.g., a connection port) of the Ethernet network device; a transmitter of the network device transmits transmission signals via another connection terminal (e.g., a connection port) of the Ethernet network device, and the transmission signals interfere with the reception signals; the reception rate of the receiver is 2.5 Gbit/s, and the transmission rate of the transmitter is also 2.5 Gbit/s; the reception clock of the receiver is 200 MHz (i.e., symbol rate, also known as baud), the transmission clock of the transmitter is 200 MHz plus a bias (i.e., symbol rate, also known as baud), and the oversampling circuit 210 generates the oversampled signal according to a clock twice as fast as the transmission clock so that the frequency of the oversampled signal is the double of the frequency of the transmission clock and is higher than the frequency of the reception clock.
- a connection terminal e.
- the reception rate of the receiver is 2.5 Gbit/s and the transmission rate of the transmitter is 1 Gbit/s; the reception clock is 200 MHz, the transmission clock is 125 MHz plus a bias, and the oversampling circuit 210 generates the oversampled signal according to a clock twice as fast as the transmission clock so that the frequency of the oversampled signal is the double of the frequency of the transmission clock and is higher than the frequency of the reception clock.
- the configuration of the oversampling circuit 210 and other exemplary implementations can be derived from the above description in view of the demand for implementation.
- the clock difference calculating circuit 220 of FIG. 2 can be realized with a known or self-developed technique.
- the clock difference calculating circuit 220 compares a first number of the reception clock (RX CLK ) within a period of time with a second number of the transmission clock (TX CLK ) within the same period of time, and thereby obtains a ratio of the first number to the second number indicative of the clock difference.
- the clock difference calculating circuit 220 can calculate “x” of the ratio
- the clock difference calculating circuit 220 can calculate “y” of the ratio
- FIG. 3 shows an embodiment of the sample rate converter 230 of FIG. 2 .
- the sample rate converter 230 of FIG. 3 includes a sample selector 310 and an interpolator 320 .
- the sample selector 310 is configured to selecting K output value(s) of the oversampled signal according to the clock difference and thereby generate a selection result (SEL), wherein the K is a positive integer.
- the interpolator 320 is configured to receive the selection result and perform interpolation according to the clock difference and the oversampled signal so as to generate K output value(s) of the conversion signal corresponding to the K output values of the oversampled signal.
- the frequency of the conversion signal is equal to the frequency of the reception clock for realizing the symbol rate conversion from the transmission rate to the reception rate.
- the frequency of the transmission clock is 125 MHz
- the frequency of the oversampled signal is 250 MHz
- the frequency of the reception clock is 200 MHz.
- the ratio of a quantity of output values of the oversampled signal within a period of time to a quantity of output values of the conversion signal within the same period of time is 1.25
- the time for the sample rate converter 230 receiving five output values of the oversampled signal should be equal to the time for the sample rate converter 230 outputting four output values of the conversion signal.
- the sample selector 310 can select the first four output values (In( 1 ), In( 2 ), In( 3 ), In( 4 )) among the successive five output values (In( 1 ), In( 2 ), In( 3 ), In( 4 ), IN( 5 )) of the oversampled signal (i.e., the aforementioned K output values of the oversampled signal) in accordance with the clock difference, and thereby generate the selection result without the fifth output value (In( 5 )); the interpolator 320 receives all output values of the oversampled signal and the selection result and thereby performs interpolation according to the clock difference and the oversampled signal so as to generate four output values (Out( 1 ), Out( 2 ), Out( 3 ), Out( 4 )) of the conversion signal corresponding to the four output values (In( 1 ), In( 2 ), In( 3 ), In( 4 )) of the oversampled signal.
- the interpolator 320 receives all output values of the oversampled
- the time interval between every two adjacent output values of the oversampled signal is T IN1
- the timing of Out( 1 ) is aligned with the timing of In( 1 )
- the interpolator 320 can learn that the timing difference between Out( 2 ) and In( 2 ) is 0.25T IN1
- the timing difference between Out( 3 ) and In( 3 ) is 0.5T IN1
- the timing difference between Out( 4 ) and In( 4 ) is 0.75T IN1 according to the clock difference; therefore, the interpolator 320 can use the above-mentioned timing relation and a known or self-developed interpolation algorithm to choose suitable output values of the oversampled signal and thereby generate the four output values (Out( 1 ), Out( 2 ), Out( 3 ), Out( 4 )) of the conversion signal.
- the interpolator 320 may merely receive/use some output values of the oversampled signal and perform interpolation according to the clock difference and the received/used output values.
- the frequency of the transmission clock is 200.02 MHz
- the frequency of the oversampled signal is 400.04 MHz
- the frequency of the reception clock is 200 MHz.
- the ratio of a quantity of output values of the oversampled signal within a period of time to a quantity of output values of the conversion signal within the same period of time is 2.0002
- the time for the sample rate converter 230 receiving 20002 output values of the oversampled signal should be equal to the time for the sample rate converter 230 outputting 10000 output values of the conversion signal ideally.
- the sample selector 310 can select 10000 output values (e.g., selecting In( 1 ), In( 3 ), In( 5 ), In( 19996 ), In( 19998 ), and In( 20002 ) and skipping In( 2 ), In( 4 ), In( 6 ), In( 19999 ), In( 20000 ), and In( 20001 )) among the 20002 output values of the oversampled signal (i.e., the aforementioned K output values of the oversampled signal) according to the clock difference, and thereby generate the selection result; the interpolator 320 receives all output values of the oversampled signal and the selection result and thereby performs interpolation according to the clock difference and the oversampled signal so as to generate 10000 output values (Out( 1 ), Out( 2 ), Out( 9999 ), Out( 10000 )) of the conversion signal that are corresponding to the 10000 output values (In( 1 ), In( 3 ), In( 5 ), In( 19996 ), In( 1999
- the time interval between every two adjacent odd/even output values of the oversampled signal is T IN2
- the timing of Out( 1 ) is aligned with the timing of In( 1 )
- the interpolator 320 can find out that the timing difference between Out( 2 ) and In( 3 ) is 0.0002T IN2
- the timing difference between Out( 3 ) and In( 5 ) is 0.0004T IN2
- the interpolator 320 can use the above-mentioned timing relation and a known or self-developed interpolation algorithm to generate the 10000 output values (Out( 1 ), Out( 2 ), Out( 9999 ), Out( 10000 )) of the conversion signal.
- the selection of the output values of the oversampled signal may be related to the accumulation of timing difference and the cycle of signal correspondence, and this explains why the output values “ . . . In( 19996 ), In( 19998 ), and In( 20002 )” instead of “ . . . In( 19997 ), In( 19999 ), and In( 20002 )” are selected.
- the receiver in the network device including the interference canceller 200 enters the quiet state of the low power idle mode of Energy-Efficient Ethernet (EEE); when the receiver leaves the quiet state (e.g., the network device enters a refresh state or an idle state from the quiet state), the sample rate converter 230 can refer to the clock difference, a duration of the quiet state of the low power idle mode, and a signal correspondence relation between the conversion signal and the oversampled signal at the moment the receiver enters the quiet state (e.g., before the entrance to the quiet state, the sample rate converter 230 outputs an output value Out( 5000 ) of the conversion signal corresponding to an output value In( 10000 ) of the oversampled signal) to recover the current signal correspondence relation and generate the conversion signal.
- EEE Energy-Efficient Ethernet
- the sample rate converter 230 can refer to the clock difference, the duration of the quiet state, and the output value at the moment the receiver enters the quiet state to estimate which of the output values of the conversion signal should be outputted, and thereby generate the conversion signal. Since the states of the low power idle mode recited in the specification of EEE is known in this technique field, their detail is omitted here.
- the cancelling circuit 240 is a least mean square (LMS) filter or a recursive least square (RLS) filter.
- the cancelling circuit 240 can adjust one or more coefficients of the cancelling circuit 240 according to the variation in the error signal, and thereby reduce the error which the next error signal will indicate. The smaller the error, the better the result of interference cancellation.
- the cancelling circuit 240 is included in the aforementioned network device; and the earlier the cancelling circuit 240 receiving the error signal, the better the performance
- it is preferred to have more setting values of the step size of the cancelling circuit 240 e.g., the step size of an LMS filter for accurately dealing with different interference cancellation conditions.
- FIG. 6 An embodiment of the receiver mentioned in FIG. 2 is shown in FIG. 6 , and includes a first circuit 610 , a slicer 620 , and a second circuit 630 .
- the first circuit 610 e.g., adder/subtractor
- the slicer 620 is configured to generate a series of signal levels as an output signal (RXD OUT ) according to the input signal.
- the second circuit 630 (e.g., adder/subtractor) is configured to output the error signal (S ERROR ) to the cancelling circuit 240 according to the difference between the input signal and the output signal.
- the less the difference between the input signal and the output signal the less the error which the error signal will indicate.
- FIG. 7 shows another embodiment of the interference canceller of the present disclosure.
- the interference canceller 700 of FIG. 7 further includes a calculation and statistics circuit 710 ; it should be noted that the path between the sample rate converter 230 and the calculation and statistics circuit 710 in FIG. 7 is optional in accordance with the demand for implementation.
- the calculation and statistics circuit 710 is coupled to the sample rate converter 230 and the cancelling circuit 240 , and configured to assist in making the energy variation trend of the conversion signal be identical/similar to the energy variation trend of the XPAN transmission signal as shown in FIG. 8 a so that the workload of the cancelling circuit 240 can be reduced.
- the cancelling circuit 240 has to spend more time and calculation resource to adjust the coefficient(s) of the cancelling circuit 240 , and take more efforts to generate a suitable cancellation signal for cancelling the interference component of the XPAN transmission signal according to the conversion signal.
- the clock difference is composed of a main difference and a bias; for example, if the frequency of the transmission clock is 200.02 MHz and the frequency of the reception clock is 200 MHz, the main difference is indicative of the difference between the integral parts of the two frequencies (i.e., 1200 MHz-200 MHz
- 0), and the bias is indicative of the difference between the decimal parts of the two frequencies (i.e.,
- 0.02 MHz).
- the sample rate converter 230 is configured to process the oversampled signal according to the main difference and the bias in an operation mode and thereby generate the conversion signal (e.g., FIG.
- the frequency of the conversion signal is equal to the frequency of the reception clock in the operation mode.
- the sample rate converter 230 is optionally configured to process the oversampled signal according to the main difference without referring to the bias in a calibration mode, and thereby generate the conversion signal (e.g., simply outputting the odd/even output values of the oversampled signal as the output values of the conversion signal in an alternative embodiment based on FIG. 5 ), so that the cancelling circuit 240 can promptly use the conversion signal to output a cancellation signal having an energy variation trend approaching to the energy variation trend of the XPAN transmission signal, wherein the frequency of the conversion signal is also equal to the frequency of the reception clock in the calibration mode.
- the calculation and statistics circuit 710 is used for performing the steps of FIG. 9 as follows:
- the calculation and statistics circuit 710 is configured to perform the steps of FIG. 10 in the operation mode.
- the steps of FIG. 10 are as follows:
- FIG. 11 shows an embodiment of the method for cancelling interference of the present disclosure.
- This embodiment is performed by a network device (e.g., the network device 100 of FIG. 1 ), and can generate a cancellation signal for reducing cross port alien near-end (XPAN) crosstalk of a reception signal received by a receiver of the network device.
- the embodiment includes the following steps:
- the interference canceller and the method of the present disclosure make the cancellation signal include aliasing and phase shift similar to the to-be-cancelled component of the reception signal and thereby achieve better performance of interference cancellation in comparison with the prior art especially when the timing difference between the transmitter's clock domain and the receiver's clock domain is serious.
- the interference canceller and the method of the present disclosure can track the variation in the relation between the interference signal and the cancellation signal during the low power idle mode of EEE.
Abstract
Description
that is equivalent to the ratio of “200 MHz” to “200 MHz+bias”, to indicate the clock difference. For another example, provided the frequency of the reception clock is 200 MHz and the frequency of the transmission clock is 125 MHz plus a bias, the clock
that is equivalent to the ratio of “200 MHz” to “125 MHz+bias” to indicate the clock difference. The implementation of the clock
that is dependent on the clock difference. Accordingly, the time for the
that is indicative of the double of the clock difference. Accordingly, the time for the
- S910: in the calibration mode, calculating and recording strength of the cancellation signal according to a first time interval after a predetermined time from the beginning of the calibration mode, and thereby obtaining M records, wherein the M is an integer greater than two. During the predetermined time, the variation in the cancellation signal will converge as the cancelling
circuit 240 continually adjusts the coefficient(s) of the cancellingcircuit 240 according to the aforementioned error signal, which means that the energy variation trend of the cancellation signal will become close to the energy variation trend of the XPAN transmission signal. For example, provided the frequency of the transmission clock is 200.02 MHz and the frequency of the reception clock is 200 MHz, the time length of outputting 10001 output value of the XPAN transmission signal should be equal to the time length of outputting 10000 output value of the cancellation signal; accordingly, the calculation andstatistics circuit 710 can treat the time length of outputting 500 output values as the first time interval, then calculate and record the strength of the cancellation signal according to the first time interval, and obtain at least twenty records (i.e., 10000/500) as the samples of at least 10000 output values of the cancellation signal that are corresponding to 10001 output values of the XPAN transmission signal, wherein the twenty records includes a maximum value. It should be noted that the way to calculate signal strength is known in this technical field, and the detail is omitted here. - S920: obtaining an energy variation trend of the cancellation signal according to the M records and outputting the energy variation trend (PWTREND) (i.e., the result of calculation and statistics) of the cancellation signal to the
sample rate converter 230, wherein thesample rate converter 230 generates the conversion signal according the energy variation trend of the cancellation signal as the operation mode starts, and the energy variation trend of the conversion signal is supposed to approach the energy variation trend of the cancellation signal (i.e., the energy variation trend of the XPAN transmission signal) in the operation mode. For example, provided the frequency of the transmission clock is 200.02 MHz and the frequency of the reception clock is 200 MHz, the calculation andstatistics circuit 710 provides 20 records indicative of a time length being equal/proportional to a cycle of the energy variation trend of the cancellation signal; thesample rate converter 230 finds out that the 6th record among the 20 records has the maximum value according to the output of the calculation andstatistics circuit 710; afterwards, at a time point that the energy of the cancellation signal is believed to reach the peak, thesample rate converter 230 uses the oversampled signal to perform interpolation according to the clock difference (i.e., the major difference and bias) and the position (i.e., 6/20=0.3) of the peak in the cycle of the energy variation trend, and thereby generates the maximum value (e.g., the 3000th (10000×0.3) output value “Out(3000)” that can be derived fromFIG. 5 ) of the conversion signal so as to make the energy variation trend of the conversion signal be identical/similar to the energy variation trend of the XPAN transmission signal and ensure the performance of the cancellingcircuit 240.
- S1010: calculating and recording strength of the conversion signal and the strength of the cancellation signal according to a second time interval and thereby determining whether the energy variation trend of the conversion signal deviates from the energy variation trend of the cancellation signal. The second time interval can be the same as or different from the aforementioned first time interval, and the way to calculate and record signal strength can be inferred from the description of the embodiment of
FIG. 9 . - S1020: on condition that the energy variation trend of the conversion signal deviates from the energy variation trend of the cancellation signal, informing the
sample rate converter 230 to make thesample rate converter 230 adjust the generation of the conversion signal according to the energy variation trend of the cancellation signal and thereby make the energy variation trend of the conversion signal approach the energy variation trend of the cancellation signal. The way to adjust the generation of the conversion signal can be inferred from the description of the embodiment ofFIG. 9 .
- S1110: oversampling an XPAN transmission signal originated from a transmitter of the network device and thereby generating an oversampled signal having a frequency higher than a frequency of a reception clock of the receiver. This step can be performed by the
oversampling circuit 210 ofFIG. 2 /7. - S1120: calculating a clock difference between a transmission clock of the transmitter and the reception clock of the receiver. This step can be performed by the clock
difference calculating circuit 200 ofFIG. 2 /7. - S1130: processing the oversampled signal according to the clock difference and thereby generating a conversion signal having a frequency lower than the frequency of the oversampled signal and equal to the frequency of the reception clock. This step can be performed by the
sample rate converter 230 ofFIG. 2 /7. - S1140: using a filter to generate the cancellation signal according to the conversion signal and to determine at least one coefficient of the filter according to an error signal dependent on a difference between the XPAN crosstalk of the reception signal and the cancellation signal. An embodiment of the filter is the cancelling
circuit 240 ofFIG. 2 /7.
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TW202125995A (en) | 2021-07-01 |
US20210184757A1 (en) | 2021-06-17 |
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